Middle English creole hypothesis

The Middle English creole hypothesis is a proposal that Middle English was a creole, which is usually defined as a language that develops during contact between two groups speaking different languages and that loses much of the grammatical elaboration of its source languages in the process. The vast differences between Old English and Middle English, and English's status as one of the least structurally elaborated of the Germanic languages, have led some historical linguists to argue that the language underwent creolisation at around the 11th century, shortly after the Norman conquest of England.

Source: Wikipedia — Middle English creole hypothesis (CC BY-SA 4.0)